const koa = require('koa')
const app = new koa()

app.use((ctx, next) => {
  console.log(1)
  next()
  console.log(2)
})
app.use((ctx, next) => {
  console.log(3)
  next()
  console.log(4)
})
app.use((ctx, next) => {
  console.log(5)
  next()
  console.log(6)
})

app.listen(3000, () => {
  console.log('服务已启动')
})
